The numbers on the about page are real

There are six numbers across the top of the about page now: people online right now, visitors yesterday, counters in use, countries in the last thirty days, designs to choose from, and the year this started. All six come out of the running system, and two of them move while you are looking at the page.

That is worth explaining, because a number on a page like that is usually not one.

Where each one comes from

Online right now is everybody seen on any site carrying a counter within the last five minutes. One query against a small table, six tenths of a millisecond, so the page asks it fresh every time somebody opens it.

Visitors yesterday is the number of distinct visitors across all counters for the whole of yesterday. Yesterday rather than today, because half a day is not a figure you can compare with anything. Eleven milliseconds, also asked on every request.

Counters in use and countries are the expensive pair. Counting the counters that recorded something in the last thirty days takes just under nine tenths of a second on this hardware; the distinct countries take two tenths. Asking either one on every page view would spend a second of database time on a number that moves by one between visits. They are worked out once a day and kept in a small file next to the code.

Designs comes out of the same file that builds the gallery, so it cannot drift away from what you can actually pick — right now 473. 2006 is the year of the oldest counter still in the table. 18 November, if you want the day.

Counters in use, not counters ever created

This is the one where whoever runs a service gets to choose what to say, so here is the choice.

379,174 counter numbers have been handed out since 2006. 2,124 of them recorded a visit in the last thirty days. The first number is bigger, and it is also true, and it describes a filing cabinet. The second one describes what is running. The second one is on the page, and the label underneath says which of the two it is.

Two small things about doing it this way

The cached pair carries the date it was worked out for. When that date is no longer today the page recalculates — and writes the new date before it starts rather than after. Otherwise two people opening the page in the same second after midnight would both set off the slow queries, and on a machine that gives every open connection its own process that turns into a slow page for everybody else.

If a query fails, the tile disappears rather than showing a zero. A zero would be a claim.

The rest of the page

It was rewritten at the same time: what the counter actually is, what ends up on your statistics page, what happens to a visitor's data, an honest comparison with the usual kind of analytics script, and the questions people send us most often. It is now translated into all eleven languages instead of five.

Some of what used to be on that page came off it, and that turned out to need its own post.